The invention uses the scanning laser ophthalmoscope proper of co-pending application, Ser. No. 08/178,777, filed 1994 Jan. 7.
1. Background-Field of Invention
This invention relates generally to instruments for examining the eye and specifically to an electro-optical ophthalmoscope for providing simultaneously a precise visual representative of the eye fundus, anterior eye segment, and eye functioning on a display monitor.
2. Background-Description of Prior Art
The ophthalmoscope is well known as an important aid for studying and examining the eye, and in particular, the fundus of the eye. As a result of great interest in preserving man's eyesight, ophthalmoscopes of various constructions have been built and used. The latest version of the ophthalmoscope, a scanning laser ophthalmoscope, is particularly appealing because of its unique capability of combining the visualization of the retina or eye fundus with certain psychophysical and electrophysiological testing procedures, used in studying the subjective or objective functioning of the visual pathways, from the retina to the brain cortex. With the scanning laser ophthalmoscope, a unique, precise correlation between retinal anatomy and function is established. Many different stimuli that are used in visual psychophysics, can be projected onto the fundus with the help of the scanning laser ophthalmoscope. Computer red overlay graphics are then used to display the stimulus characteristics such as size, location, and intensity on the fundus image in real-time. Detailed functional mapping of the fundus is thereby possible. Such functional mapping that is currently possible emulates classic Goldmann kinetic perimetry and automated static perimetry under light-adapted testing conditions. Until the invention, the scanning laser ophthalmoscope, has been limited to the examination of the posterior segment, excluding simultaneous imaging of both the retina, with presentation of psychophysical stimuli, and iris plane . Visualization of the anterior segment is however important because it allows an unambiguous observation of the entrance pupil of the Maxwellian view illumination used by the scanning laser ophthalmoscope. This is very significant since light entering near the center of the pupil is more efficient in eliciting a visual response than is light entering peripheral regions of the pupil. Not knowing the entrance pupil therefore precludes such testing as dark-adaptation, measuring dark-adapted thresholds and the Stiles-Crawford functions with the scanning laser ophthalmoscope.
Furthermore, eye movements and changes in the subject's fixation have hitherto limited the accuracy and ease of performing high resolution perimetry or microperimetry on the fundus. In practice, repeat trial and error presentation of one stimulus to one specific retinal location, using fiducial landmarks as a guide, can result in a waste of time, discomfort, decreased performance and limited information from the testing. The entrance pupil of the Maxwellian view is even more difficult to control manually since no reliable fiducial landmarks are available in the pupillary area.